X ray (X-ray) of the gallbladder and biliary channels, following the administration of a radiopaque dye, one of the techniques of diagnostic imaging (q.v.). In oral cholecystography, the dye is ingested, absorbed by the intestine, and concentrated by the gallbladder, which normally appears well opacified in the X ray. Abnormalities (e.g., gallstones) may be demonstrated by radiolucent areas. Oral cholecystography is usually indicated in cases of suspected gallbladder disease. Newer dyes that permit visualization of the bile channels without concentration by the gallbladder are administered intravenously to determine or rule out the presence of intermittent obstruction of the bile ducts or recurrent biliary disease after biliary surgery.